The meter does put a load on the batterys so you get a more accurate reading vs. get a high floating voltage reading and thats what you want. If you don't mind seperate tach and meter you could also look at the Hobbico meter. Its similiar and tells you if its safe to fly or if its time to recharge. Check out the link below to look at it. I also use a Super Test battery tester now and then to find out exactly how good the batterys are doing.
http://www2.towerhobbies.com/cgi-bin...&I=LXWW16&P=ML
http://www.californiasailplanes.com/supertest.html[8D]